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6-23. Voltage Controlled Crystal Oscillator Test
This test checks the circuits in the signal path shown in Figure 6-15. The circuits that are
specifically tested are the Voltage Controlled Crystal Oscillator (including two adjustments),
the Loop Shaping Control, and the Lock Detector. A signal is input to the IF Input from an
-hp- 3325A opt 001. First, the Channel B output is measured with a counter while the VCO
center frequency is adjusted; this is done with L12 open. Then, the Channel B output is
measured with a scope while the VCO tuning range is adjusted; this is done with L12 closed.
The test passes if the adjustments can be made. The results are printed.
Initializing the Test
With the Low Frequency Menu displayed, press SFK K2 to initialize the test. After initializa
tion, follow the instructions displayed on the computer.
What if the Test Fails?
Assuming the previous tests have passed, the most probable cause of failure will be one of
the following:
• theVCxO
• the Loop Shaping Control
• the Lock Detector
• the associated switches and their driving circuits
Refer to Service Group One for schematics, component locators, and circuit descriptions.
The subprogram "SWITCH" can be helpful in isolating the problem.
Equipment Set Up
Set Up For A3R324 Adjustment
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